Method of sterilizing anthers of plants

ABSTRACT

A method is provided for sterilizing anthers of plants, such as Gramineae or Helianthus annuus (sunflower) by applying a sterilizing agent to the plants at the fifth and/or sixth stage of organogenesis, chosen from among terpenoid compounds of the methylcyclohexene series.

BACKGROUND OF THE INVENTION

1. Field of the Art

The present invention relates to the art of biology and agriculture and,more particularly, to a method of sterilizing anthers of plants which isused in selection and seed production.

2. Description of the Prior Art

At the present time the world is facing the problem of intensificationof agriculture, in particular of raising yields of grain crops, fodder,vegetable and industrial plants by way of an extensive application ofthe first-generation hybrids. Due to the heterosis phenomenon thesehybrids are distinguished from the parental forms by a higher (by25-30%) productivity and a better quality of the products. Known is amethod for breeding novel hybrids which is based on a "cytoplasmic malesterility-fertility reductants" system. This method is based on along-term (12-14 years) and complicated selection work involving thecreation of sterile analogs, sterility-fixing agents and fertilityreductants. Most promising are methods based on sterilization of anthersof plants by chemical sterilizing agents (gametocides). The use ofgametocides proves to be much more economically efficient than the useof the "cytoplasmic male sterility" system, since there is no necessityin creating such forms as a sterile analog, an analog of sterilityfixation in maternal forms and an analog of fertility reduction inpaternal ones. In fact it is possible to obtain seeds of thefirst-generation hybrids both in the course of the selection studying ofthe initial forms and in the organization of their industrialproduction.

By now about 200 compounds have been found which display a gametocidalactivity and belong to different classes of chemical compounds asregards their chemical structure. Gametocides must cause maximum fullmale sterility in the treated plants, while preserving the viability ofovicells and ensuring settability in free pollination at a sufficientlyhigh level (preferably not less than 70% of the control). Theirphytotoxicity and toxicity for the warm-blooded must be minimal.

Known in the art are methods of sterilizing the anthers of gramineouscrops (L. J. Nickell. Plant Growth Regulators. Applications inAgriculture. Moscow, "Kolos" Publishers, 1984, pp. 28-31; SU, A, No.906457) which comprise treating the plants with sterilizing agents suchas 2-chloroethylphosphonic acid (Ethrel), maleic acid hydrazide,di-(polyfluoroalkyl)-phosphoric acids and salts thereof and the like.The treatment of the plants with the sterilizing agents is effected atthe V-th or VI-th stage of organogenesis (after F. M. Kuperman).

At the V-th stage of organogenesis the processes of the formation anddifferentiation of florets begin. At the end of this stage neoplasmsoriginate: sporogeneous archisporeal tissues. At this stage theinitiation of stamina, pistil and integumentary organs of the floretoccurs. At the V-th stage the beginning of differentiation of the stamenprimordium into a connective and pistil is observed. The VI-th stage ischaracterized by the processes of the floret formation (micro- andmacro-sporogenesis). At this stage individual mononuclear pollen grainsare usually formed (F. M. Kuperman, "Morphophysiology of Plants",Moscow, "Vysshaya Shkola" Publishers, 1973, pp. 30-36).

Also known in the art is a method of sterilizing the anthers ofgramineous plants (GB, A, No. 1567153), which comprises treating thegramineous plants with a sterilizing agent during the period between theappearance of the second internode and earing. As the sterilizing agentuse is made of heterocyclic compounds, the main representatives thereofbeing 2-carboxy-3,4-methanopyrrolidine or2-methoxycarbonyl-3,4-methanopyrrolidine. These compounds are used incombination with diluents and surfactants.

SUMMARY OF THE INVENTION

The present invention is directed to the selection of novel sterilizingagents and to a method enabling its application for sterilization ofanthers of a wide range of crops with a high efficiency ofsterilization, while preserving a high settability of seeds in openpollination.

This object is accomplished by provides a method of sterilizing anthersof plants by way of treatment thereof with a sterilizing agent incombination with a diluent during the period of the fifth and/or sixthstage of Organogenesis. In accordance with the present invention, as thesterilizing agent use is made of terpenoid compounds of the generalformula: ##STR1## or mixtures thereof. The sterilizing agent can be usedin combination with any known acceptable diluent. It is advisable to useit in combination with water in the form of a 0.1-2% aqueous emulsion.As the plants to be treated with the above-specified sterilizing agent,it is preferable to use gramineous plants or sunflower.

The method according to the present invention makes it possible toattain male sterility of the plants (98-100%) and to retain a highpercentage of settability of seeds (above 70%). In order to ensure ahigh level of sterilization of anthers under non-favourable climaticconditions, a repeated treatment of the plants with the sterilizingagent is carried out during the periods of the fifth and/or sixth stageof organogenesis (after Kuperman).

PREFERRED EMBODIMENT OF THE INVENTION

The method according to the present invention is carried out in thefollowing manner.

Plants such as winter and spring wheat, diploid and tetraploid rye,triticale, millet, sunflower are treated with a sterilizing agent; assuch an agent use is made of terpenoid compounds of the general formula:##STR2## or mixtures thereof. The terpenoid compounds can be used incombination with any acceptable diluents. It is advisable to use wateras the diluent. It is preferable to use a 0.1-2% aqueous emulsion of theabove-mentioned compounds.

When desired, any suitable surfactants can be added to the workingsolutions. Usually it is advisable to add any known auxiliary additivessuch as wetting agents, dispersing agents, adhesives to the workingsolutions while applying them to the plants.

The sterilizing agent can be applied to the plants by various treatmentmethods such as hydraulic spraying, or air spraying (aerosols). Thetreatment of the plants with the sterilizing agent is carried out duringthe period of the fifth and/or sixth stage of organogenesis (afterKuperman). The dose of the sterilizing agent depends on the nature ofthe compound, the crop being treated, the stage of the treatment and onthe natural climatic factors. In order to ensure a high sterilizingeffect under unfavourable climatic conditions, it is advisable thatrepeated treatment of the plants be carried out at the VI-th stage oforganogenesis. The total dose of the sterilizing agent is varied withinthe range of 0.6 to 20 kg/ha.

All the terpenoid compounds according to the present invention, whichare employed as the sterilizing agent have been tested for toxicity inexperiments on animals. The results of the experiments have shown thatthese compounds are low-toxic or substantially non-toxic.

Thus, the LD₅₀ of α-terpeniol is 4,300 mg/kg, while the LD₅₀ of α-pineneis 3,700 mg/kg.

All the terpenoid compounds according to the present invention arenaturally-occurring compounds which are obtained from the gum ofconiferous plants.

The presence of the gametocidal activity in the sterilizing agentsaccording to the present invention has been revealed in field tests indifferent soil and climatic zones on 10 m² plots in 2-3 and 4-foldtiers. Each sterilizing agent has been tested for at least 5 years.

The occurrence of the organogenesis stages is controlled cytologically.The treatment of the plants with the sterilizing agent is carried out atthe beginning of the fifth stage of organogenesis according to Kuperman.

In the course of earing, the main ears and other tiers are isolated bymeans of parchment isolators. For wheat and triticale individualisolators are used. For rye 1 ear from 5 to 7 different adjacent plantsis brought under one common isolator. For millet each panicle isisolated individually. The percentage of sterility (X) for wheat, rye,triticale and millet is calculated according to the formula: ##EQU1##

The number of seeds in the non-isolated ears of the control plants isassumed to be a 100% settability in open pollination.

To obtain reliable data, 20-25 isolators are used from each tier forwheat and triticale, 10-15 isolators from each tier are used for rye andmillet.

To control the chemical sterilization of sunflower pollen, 45 treatedplants on each tier are used for each compound, of which 15 plants areisolated for self-pollination, the heads of 15 other plants arepollinated with a mixture of pollen gathered on 20-25 treated isolatedheads, and 15 plants are left for open pollination to check thesettability of the achenes with the paternal-form pollen.

The male sterility of sunflower plants is evaluated by the results offertility and viability of pollen, morphological features of spermatozoaand settability of achenes when pollinating the treated isolated plantswith pollen of the non-treated parental form. The viability of theovicell is determined from the setting of seeds in the treated plants inopen pollination with the paternal-form pollen.

The treatment of plants should be preferably carried out in clear calmweather. All the compounds penetrate into the plant tissues within theperiod of 4 hours. In the case of rainfall during the 4-hours' period arepeated treatment of the plants at the VI-th stage of organogenesis isnecessary.

For a better understanding of the present invention, some specificexamples illustrating the embodiments of the method according to theinvention are given hereinbelow.

EXAMPLES 1 TO 6

Plants of winter wheat of Mironovskaya 808 variety are treated at theV-th stage of organogenesis (after Kuperman) by way of spraying, from aknap-sack sprayer, with a 2% aqueous emulsion of the followingsterilizing agents: 1-n-mentene-8-ol, 1-n-mentenyl-8-acetate, 3-carene,1,-4-(8)-n-mentadiene, 1,8-n-mentadiene, n-cymene respectively. As theemulsifying agent use is made of 0.1% by mass of a calcium C₁₂ -C₁₄-alkylbenzene sulphonate. As the adjuvant introduced into the emulsionis 0.01% by mass of dodecylsulphate. The rate of consumption of thepreparation is 12 kg/ha. Serving as the control are the plants treatedwith the diluent without the sterilizing agent. The results of the testsare shown in Table 1 hereinbelow. Similar results are obtained in thetreatment of the plants at the VI-th stage of organogenesis.

EXAMPLES 7 TO 13

Plants of spring wheat of Moskovskaya 35 variety are treated at theVI-th stage of organogenesis with a 1% aqueous emulsion of the followingsterilizing agents:

                  TABLE 1                                                         ______________________________________                                                                               Percentage                                            Number          Number of                                                                             of setting                                            of grains       grains in                                                                             of seeds                                              in ear   Sterility                                                                            ear in  in open                                     Example   under    percent-                                                                             open polli-                                                                           pollina-                               No.  No.       isolator age, % nation  tion, %                                ______________________________________                                        1    Control   40.6      0.0   42.6    100.0                                  2    Example 1 0.0      100.0  40.1    94.1                                   3    Example 2 0.0      100.0  38.8    91.1                                   4    Example 3 0.0      100.0  39.7    93.2                                   5    Example 4 0.6      98.5   40.2    94.4                                   6    Example 5 3.8      90.7   41.8    98.1                                   7    Example 6 0.7      98.3   39.9    93.7                                   ______________________________________                                    

α-terpeniol, 1-n-mentenyl-8-acetate, 3-carene, 1,-4-(8)-n-mentadiene,1,8-n-mentadiene, n-cymene, α-pinene respectively. The emulsioncontains, as the emulsifying agent, 0.1% by mass of a calcium C₁₂ -C₁₄-alkylbenzene sulphonate and as the adjuvant -0.01% by mass ofN,N-dimethylformamide. The rate of consumption of the preparation is 8kg/ha. Serving as the control are the plants treated with the diluentwithout the sterilizing agent. The results of the tests are shown inTable 2 hereinbelow. Similar results have been obtained in the treatmentof the plants at the V-th stage of organogenesis.

EXAMPLES 14-20

Plants of spring wheat of Botanicheskaya 4 variety are treated at theV-th stage of organogenesis with a 1% aqueous emulsion of the followingsterilizing agents: 3-carene, n-cymene, α-pinene, α-terpeniol,1,-4-(8)-n-menyadiene, 1,8-n-mentadiene, 1-n-mentenyl-8-acetaterespectively. The emulsion contains, as the emulsifying agent, 0.1% bymass of a calcium C₁₂ -C₁₄ -alkyl-benzene sulphonate and, as theadjuvant -0.01% by mass of tetrahydrofuran. The rate of consumption ofthe preparation is 6 kg/ha. Serving as the control are the plantstreated in a manner similar to that described in Example 1 hereinbefore.The results of the tests are shown in Table 3. Similar results areobtained in the treatment of the plants in the VI-th stage oforganogenesis.

                  TABLE 2                                                         ______________________________________                                                       Number          Number of                                                                             Percentage                                            of grains       grains in                                                                             of grain                                              in ear   Sterility                                                                            ear in  setting in                                  Example   under    percent-                                                                             open polli-                                                                           open pol-                              No.  No.       isolator age, % nation  lination, %                            ______________________________________                                        1.   Control   29.4      0.0   31.2    100.0                                  2.   Example 7 0.0      100.0  27.2    87.2                                   3.   Example 8 0.0      100.0  28.6    91.7                                   4.   Example 9 0.2       99.3  29.0    92.9                                   5.   Example 10                                                                              0.0      100.0  28.1    90.1                                   6.   Example 11                                                                              0.8       97.3  30.0    96.2                                   7.   Example 12                                                                              1.2       95.9  27.3    87.5                                   8.   Example 13                                                                              0.0      100.0  28.7    91.0                                   ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                       Number          Number of                                                                             Percentage                                            of grains                                                                              Percent-                                                                             grains in                                                                             of grain                                              in ear   age of ear in  setting in                                  Example   under    sterility,                                                                           open polli-                                                                           open pol-                              No.  No.       isolator %      nation  lination, %                            1    2         3        4      5       6                                      ______________________________________                                        1.   Control   28.9      0.0   30.9    100.0                                  2.   Example 14                                                                              0.0      100.0  27.8    90.0                                   3.   Example 15                                                                              1.2       95.9  30.1    97.4                                   4.   Example 16                                                                              0.0      100.0  29.2    94.5                                   5.   Example 17                                                                              0.0      100.0  28.4    91.9                                   6.   Example 18                                                                              0.0      100.0  29.5    95.5                                   7.   Example 19                                                                              0.8       97.2  27.3    88.3                                   8.   Example 20                                                                              0.0      100.0  29.5    95.5                                   ______________________________________                                    

EXAMPLES 21 to 23

Plants of diploid rye of Chulpan variety are treated at the VI-th stageof organogenesis (after Kuperman) by way of spraying, from a knap-sacksprayer, a 1.0% aqueous emulsion of 1,4-(8)-n-mentadiene,1,8-n-mentadiene or p-cymene respectively. The emulsion contains 0.1% bymass of calcium C₁₂ -C₁₄ -alkylbenzene sulphonate and 0.01% by mass ofdodecylsulphate. The rate of consumption of the sterilizing agent is 10kg/ha. Serving as the control are the plants treated in a manner similarto that described in Example 1. The results of the tests are shown inTable 4 hereinbelow. Similar results are obtained in the treatment ofthe plants at the V-th stage of organogenesis.

                                      TABLE 4                                     __________________________________________________________________________              Number of grains                                                                       Sterility                                                                           Number of grains                                                                       Percentage of grain                                   in ear under                                                                           percentage,                                                                         in ear in open                                                                         setting in open                             No.                                                                              Example No.                                                                          isolator %     pollination                                                                            pollination, %                              __________________________________________________________________________    1. Control                                                                              44.1      0.0  49.6     100.0                                       2. Example 21                                                                           0.8      97.8  47.8     96.4                                        3. Example 22                                                                           0.3      99.2  43.2     87.1                                        4. Example 23                                                                           0.0      100.0 47.4     95.6                                        __________________________________________________________________________

EXAMPLES 24-27

Plants of tetraploid rye of Ukrainskaya tetra variety are treated in amanner similar to that described in Example 1 hereinbefore. In so doing,use is made of a 1% aqueous emulsion of the following sterilizingagents: 2-pinene, α-terpeniol, terpenylacetate, 3-carene. The rate ofconsumption of the sterilizing agent is 8 kg/ha. Serving as the controlare the plants treated with the diluent without the sterilizing agent.The results of the tests are shown in Table 5 hereinbelow.

                  TABLE 5                                                         ______________________________________                                                       Number          Number of                                                                             Percentage                                            of grains       grains in                                                                             of grain                                              in ear   Sterility                                                                            ear in  setting in                                  Example   under    percent-                                                                             open polli-                                                                           open pol-                              No.  No.       isolator age, % nation  lination, %                            ______________________________________                                        1.   Control   28.0      0.0   36.8    100.0                                  2.   Example 24                                                                              0.0      100.0  36.3    98.6                                   3.   Example 25                                                                              0.4      98.6   33.8    91.8                                   4.   Control   36.1      0.0   40.2    100.0                                  5.   Example 26                                                                              0.0      100.0  32.8    81.6                                   6.   Example 27                                                                              0.1      99.6   37.3    92.8                                   ______________________________________                                    

EXAMPLES 28-29

Plants of diploid rye of Kharkovskaya 55 variety are treated, in amanner similar to that of Example 1, with a 1% aqueous emulsion of thefollowing sterilizing agents: terpenylacetate and 3-carene respectively.The rate of consumption of the sterilizing agent is 6 kg/ha. The resultsof the tests are shown in Table 6 hereinbelow.

                                      TABLE 6                                     __________________________________________________________________________              Number of grains                                                                       Sterility                                                                           Number of grains                                                                       Percentage of grain                                   in ear under                                                                           percentage,                                                                         in ear in open                                                                         setting in open                             No.                                                                              Example No.                                                                          isolator %     pollination                                                                            pollination, %                              __________________________________________________________________________    1. Control                                                                              31.5      0.0  39.4     100.0                                       2. Example 28                                                                           0.1      99.7  35.2     89.3                                        3. Example 29                                                                           0.6      98.1  36.7     93.1                                        __________________________________________________________________________

EXAMPLES 30-31

Plants of triticale of PRAG-109 variety are treated at the V-th stage oforganogenesis, in a manner similar to that of Example 1 hereinbefore,with a 2% aqueous emulsion of the following sterilizing agents:terpenylacetate and 3-carene respectively. The rate of consumption ofthe sterilizing agent is 12 kg/ha. The results of the tests are shown inTable 7 hereinbelow. Similar results are obtained in the treatment ofthe plants at the VI-th stage of organogenesis.

                                      TABLE 7                                     __________________________________________________________________________              Number of grains                                                                       Sterility                                                                           Number of grains                                                                       Percentage of grain                                   in ear under                                                                           percentage,                                                                         in ear in open                                                                         setting in open                             No.                                                                              Example No.                                                                          isolator %     pollination                                                                            pollination, %                              __________________________________________________________________________    1. Control                                                                              41.3      0.0  45.8     100.0                                       2. Example 30                                                                           0.0      100.0 40.9     89.3                                        3. Example 31                                                                           0.3       99.3 37.6     82.1                                        __________________________________________________________________________

EXAMPLES 32-33

Plants of triticale of Amphidiploid 206 variety are treated at the VI-thstage of organogenesis, in a manner similar to that described in Example1, with a 2% aqueous emulsion of the following sterilizing agents:terpenylacetate and 3-carene respectively. The rate of consumption ofthe sterilizing agent is 12 kg/ha. The results of the tests incomparison with the control are shown in Table 8 hereinbelow. Similarresults are obtained in the treatment of the plants at the V-th stage oforganogenesis.

                                      TABLE 8                                     __________________________________________________________________________              Number of grains                                                                       Sterility                                                                           Number of grains                                                                       Percentage of grain                                   in ear under                                                                           percentage,                                                                         in ear in open                                                                         setting in open                             No.                                                                              Example No.                                                                          isolator %     pollination                                                                            pollination, %                              __________________________________________________________________________    1. Control                                                                              23.4      0.0  25.2     100.0                                       2. Example 32                                                                           0.4      97.8  23.0     91.3                                        3. Example 33                                                                           0.0      100.0 23.8     94.4                                        __________________________________________________________________________

EXAMPLES 34-39

Plants of millet of Mironovskoye 94 variety are treated at the V-thstage of organogenesis, in a manner similar to that of Example 1, with a1% aqueous emulsion of the following sterilizing agents:terpenylacetate, 3-carene, 1,4-(8)-n-mentadiene, 1,8-n-mentadiene,n-cymene, α-terpeniol respectively. The rate of consumption of thesterilizing agent is 10 kg/ha. The results of the tests in comparisonwith the control are shown in Table 9. Similar results are obtained inthe treatment of the plants at the VI-th stage of organogenesis.

EXAMPLE 40

Plants of spring wheat of Botanicheskaya 4 variety are treated asdescribed in Example 1 hereinbefore at the VI-th stage of organogenesiswith a 1% aqueous emulsion of a sterilizing agent mixture, namely:1,4-(8)-n-mentadiene and n-cymene employed in the ratio of 1:1. The rateof consumption of the mixture of the sterilizing agents is 6 kg/ha. Theresults of the tests are shown in the following Table 10. Similarresults are obtained in the treatment of the plants at the V-th stage oforganogenesis.

                  TABLE 9                                                         ______________________________________                                                       Number          Number of                                                                             Percentage                                            of grains       grains in                                                                             of grain                                              in panicle                                                                             Sterility                                                                            panicle in                                                                            setting in                                  Example   under    percent-                                                                             open polli-                                                                           open pol-                              No.  No.       isolator age, % nation  lination, %                            ______________________________________                                        1.   Control   124.9     0.0   145.4   100.0                                  2.   Example 34                                                                              0.0      100.0  138.9   95.5                                   3.   Example 35                                                                              0.0      100.0   89.1   62.3                                   4.   Example 36                                                                              0.0      100.0  137.3   89.6                                   5.   Example 37                                                                              0.0      100.0  109.3   71.1                                   6.   Example 38                                                                              0.0      100.0  107.3   70.0                                   7.   Example 39                                                                              0.0      100.0  128.5   86.0                                   ______________________________________                                    

EXAMPLE 41

Plants of spring wheat of Rodina variety are treated in a manner similarto that of Example 1 at the VI-th stage of organogenesis with a 1%aqueous emulsion of a mixture of the sterilizing agents, viz. 3-careneand α-terpeniol employed in the ratio of 1:1. The rate of consumption ofthe mixture of the sterilizing agents is 6 kg/ha. The results of thetests are shown in Table 11 hereinbelow. Similar results are obtained inthe treatment of the plants at the V-th stage of organogenesis.

                  TABLE 10                                                        ______________________________________                                                       Number          Number of                                                                             Percentage                                            of grains       grains in                                                                             of grain                                    Treatment in ear   Sterility                                                                            ear in  setting in                                  of the    under    percent-                                                                             open polli-                                                                           open pol-                              No.  plants    isolator age, % nation  lination, %                            ______________________________________                                        1.   Control   28.9      0.0   30.9    100.0                                  2.   With the   0.0     100.0  27.4    88.7                                        mixture of                                                                    the                                                                           sterilizing                                                                   agents                                                                   ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                                       Number          Number of                                                                             Percentage                                            of grains       grains in                                                                             of grain                                    Treatment in ear   Sterility                                                                            ear in  setting in                                  of the    under    percent-                                                                             open polli-                                                                           open pol-                              No.  plants    isolator age, % nation  lination, %                            ______________________________________                                        1.   Control   29.5      0.0   35.0    100.0                                  2.   With the   0.0     100.0  29.4    84.0                                        mixture of                                                                    the                                                                           sterilizing                                                                   agents                                                                   ______________________________________                                    

EXAMPLES 42-44

Plants of diploid rye of Chulpan variety are treated in a manner similarto that of Example 1 at the VI-th stage of organogenesis with a 1%aqueous emulsion of the following mixtures of the sterilizing agents:2-pinene with 1.8-n-mentadiene (in the ratio of 1:1), terpenylacetatewith n-cymene (in the ratio of 1:1), 3-carene with terpenylacetate (inthe ratio of 1:1). The rate of consumption of the sterilizing agents is6 kg/ha. The results of the tests are shown in Table 12 hereinbelow.Similar results are obtained in the treatment of the plants at the V-thstage of organogenesis.

                                      TABLE 12                                    __________________________________________________________________________              Number of grains                                                                       Sterility                                                                           Number of grains                                                                       Percentage of grain                                   in ear under                                                                           percentage,                                                                         in ear in open                                                                         setting in open                             No.                                                                              Example No.                                                                          isolator %     pollination                                                                            pollination, %                              __________________________________________________________________________    1. Control                                                                              44.5      0.0  46.6     100.0                                       2. Example 42                                                                           0.0      100.0 43.3     92.9                                        3. Example 43                                                                           0.0      100.0 38.0     81.5                                        4. Example 44                                                                           0.0      100.0 46.2     99.2                                        __________________________________________________________________________

EXAMPLES 45 TO 48

Plants of sunflower of Peredovik variety and of BK-119 line are treatedin a manner similar to that described in Example 1 hereinbefore at theV-th stage of organogenesis with a 0.2% aqueous emulsion of thefollowing sterilizing agents: α-terpeniol and 3-carene respectively. Therate of consumption of the sterilizing agents is 1.2 kg/ha. The resultsof the tests are shown in Table 13 hereinbelow.

                                      TABLE 13                                    __________________________________________________________________________              Percentage                                                                    of setting                                                                             Percentage                                                                          Mass Number                                                                             Oil  Germination                                     of achenes                                                                             of setting                                                                          of   of   content                                                                            rate                                            pollination with                                                                       in open                                                                             1,000                                                                              sterile                                                                            of   of                                              the pollen mixture                                                                     pollination,                                                                        achenes,                                                                           plants,                                                                            achenes,                                                                           achenes,                              No.                                                                              Example No.                                                                          under isolator                                                                         %     g    %    %    %                                     __________________________________________________________________________    Sunflower of Peredovik variety                                                1. Control                                                                              85.0     85.0  84.0  0.0 54.7 100.0                                 2. Example 45                                                                           0.0      80.0  82.3 100.0                                                                              53.4 100.0                                 3. Example 46                                                                           0.0      85.3  84.0 100.0                                                                              53.6 100.0                                 Sunflower of BK-119 line                                                      4. Control                                                                              72.6     85.0  60.0  0.0 51.0 100.0                                 5. Example 47                                                                           0.0      80.4  55.4 100.0                                                                              49.4 100.0                                 6. Example 48                                                                           0.0      82.5  56.7 100.0                                                                              51.7 100.0                                 __________________________________________________________________________

INDUSTRIAL APPLICABILITY

The method of the invention finds application in selection and seedproduction for raising and yielding of highly productive varieties andhybrids of crops.

We claim:
 1. A method of sterilizing anthers of plants which comprisesapplying to said plants with a gametocidally effective amount of asterilizing agent in combination with a diluent during the period of thefifth and/or sixth stage of organogenesis, said sterilizing agent beinga terpenoid compound of the formula: ##STR3## or mixtures thereof.
 2. Amethod as set forth in claim 1 in which said sterilizing agent isapplied in the form of a 0.1-2.0% by weight water emulsion containing0.1-0.5% by weight of emulsifier.
 3. A method as set forth in claim 1 inwhich said plants are gramineous plants and sunflower.
 4. A methodaccording to claim 1 or 2 or 3 in which said sterilizing agent isapplied repeatedly to said plant during the period of the fifth and/orsixth stage or organogenesis to assure a high level of sterilization ofthe anthers.
 5. The method of claim 1, wherein A represents ##STR4## 6.The method of claim 1, wherein A represents ##STR5##
 7. The method ofclaim 1, wherein A represents ##STR6##
 8. The method of claim 1, whereinA represents ##STR7##
 9. The method of claim 1, wherein A represents##STR8##
 10. The method of claim 1, wherein A represents ##STR9## 11.The method of claim 1, wherein A represents ##STR10##